The invention relates to an articulated driving mechanism composed of several inflexible links in succession, the links of each pair of adjacent links being interconnected by means of a link pin, which is arranged in both the adjacent links in such a manner that the links are pivotal in relation to one another about the axis of the pin, and each pair of adjacent links being lockable against pivoting in relation to one another.
U.S. Pat. No. 3,234,698 describes a chain-like link mechanism, composed of elongated chain links. Each chain link is formed by two elongated link plates, held spaced apart in parallel by means of two transverse pins, which are rigidly connected with the link plates, for example, by welding, and are spaced apart at a distance from the respective ends of the chain link. In every second chain link, the link plates are spaced apart with a smaller distance than in the adjacent links, so that the ends of this link may be inserted between the link plates of the respective adjacent links. At the opposite ends of the link plates of each chain link, a U-shaped indentation is formed, constituting a kind of fork, which can be pushed onto the pin of an adjacent link. In this position, in which a fork at either end of each chain link is grasping a pin of each adjacent link, the chain links are unable to pivot in relation to one another. In order for the chain links to be held in this interlocking position, each chain link has plate-shaped locking members at one end, one end of which is pivotally arranged about the respective ends of the pin located at this end, and the other end of which has L-shaped cutouts, grasping around projecting ends of the closest pin of the adjacent member. In a first position of the locking member, the end of the pin is located in a leg of the L-shaped cutout, said leg being transverse relative to the chain links, so that the chain links are inseparable, since separation is only possible by displacing said chain links in their longitudinal direction away from one another. In a second position of the locking member, the end of the pin can slide along a leg of the L-shaped cutout, said leg being longitudinal relative to the chain links, so that the pins of the chain links can slide out of the respective forks of the adjacent members. In this pushed out position, adjacent links are pivotal in relation to one another, in that one link can pivot in relation to the locking member about the axis of the pin, the ends of which are arranged in the L-shaped cutouts of the locking member, and in that the other link can pivot about the axis of the pin, about the ends of which the locking members are pivotally arranged. In this position, the locking members therefore function as a kind of short chain links, holding the long links together two and two. However, as a consequence of the elongated chain links, this link mechanism is not particularly flexible, and in its flexible state it cannot be pushed into a channel, unless an end of it is pulled, because the resulting frictional resistance between the links and the channel walls would then be too great. Furthermore, the function of this link mechanism depends on its spatial orientation, because the locking members may unintentionally pivot to the unlocked position, in which the chain links are separable, for example, when advancing the link mechanism horizontally.
WO 02/064995 describes a chain composed of links, which are selectively capable of rigid engagement with one another. Each chain link is composed of two plate-like link plates spaced apart, the ends of which are pivotally connected with the adjacent link by means of a pin. The chain is alternately composed of links, the link plates of which are held at a fixed distance from one another, and links, the link plates of which are spring-loaded for abutment against the respective inner sides of the link plates of the adjacent link by means of a compression spring arranged around each pin. In the spring-loaded position, in which the link plates of the adjacent links are pressed against one another, mutually abutting meshing surfaces of the respective link plates of the adjacent links cause the links to be locked in a position, in which they are arranged in succession along a line. By passing the chain through a narrowing channel, the link plates of every second chain link, which are spring-loaded away from one another, can be pressed against one another, so that these link plates disengage from the link plates of the adjacent links, so that the adjacent links can be pivoted in relation to one another about the pins connecting them. When the spring-loaded link plates are pressed together by insertion in the narrowing channel, a rather large amount of friction, however, occurs between the link plates and the channel wall, and driving this chain therefore requires a relatively large amount of energy.
U.S. Pat. No. 4,885,907 describes a so-called chain bar composed of chain links, in which a projecting flange of a link is inserted in a fork member of an adjacent link and arranged pivotally therein about a pin. About the edges of the flange, three circular arcuated cutouts are distributed, in which the periphery of a bolt arranged in a longitudinally displaceable manner in the fork link can engage, so that the flange is lockable against rotation about the pin in three different positions. When displacing the bolt in its longitudinal direction, it can be brought into a position, in which a cutout at its periphery allows passage of the flange edges projecting between the circular arcuated cutouts, so that the chain links are free to rotate in relation to one another about the pin. Since the links are held together by the pins in the same manner as in a conventional chain, in the locked position as well, the sum of the play between the individual links will, as known, cause quite a significant backlash in the longitudinal direction of the link mechanism, and therefore it is not suitable for advancing an object accurately.
U.S. Pat. No. 6,321,945 describes a motor driven dispenser for dispensing caulking or glue material comprising a cylindrical cartridge holder, in which a conventional caulking material or glue cartridge can be inserted through an end opening of the cartridge holder. A piston is displaceable in the cartridge holder for dispensing caulking material or the like, the piston being fastened at a first end of a toothed rack, which is divided into links along part of its length. At the lateral face of the toothed rack opposite the toothing, the links are hinged to one another, so that the toothed rack is flexible. The toothed rack can be driven back and forth by a motor driven toothed wheel engaging with the toothed rack toothing, which faces downwards towards a handle of the caulking dispenser. When retracting the piston in the cartridge holder, the end of the toothed rack opposite the piston is displaced about a guide wheel, so that it follows a U-shaped path and thus does not project from the rear end of the caulking gun. However, a disadvantage of this apparatus is that the end of the flexible toothed rack opposite the piston passes across the top side of the cartridge holder, making it impossible to design this apparatus with an upwardly open cartridge holder for rapid positioning of the caulking material cartridge. Since the toothed rack is upwardly flexible when advanced in the cartridge holder, an upwardly open cartridge holder would furthermore mean that the toothed rack with the piston would not be securely fixed, when no cartridge is mounted. The hinging of the links of the toothed rack further causes a backlash when retracting the piston, but also when advancing it, since the piston is able to twist in the caulking material cartridge as a consequence of the flexibility of the toothed rack.
DE 35 13 880 describes a motor driven caulking gun, the piston of which is advanced by a chain running along a U-shaped path about a guide wheel, and the end of which, opposite the piston, is conveyed back and forth by means of a worm drive. The inherent backlash of the chain causes inaccurate controlling of the piston, both when caulking and when retracting the piston in order to prevent afterflow.